Does anyone care to ask an amplifier designer a technical question? My door is open.

Thanks for all you do as it is greatly appreciated! As a DIY tube enthusiast I would love to hear your suggestions on a good tube amp kit to build. Looking for at least 20 - 30 watts per channel. Can you point me to a place where such a kit is available for sale or at least a parts list and general instructions? A kit you would approve of in terms of sound quality and design. It would be great if you offered such at kit? Perhaps you do, but I missed it? 

Youe are really great for doing this.  I have read that James Parker (Is that the right name) of Audio Research seems to design in a bit of added second harmonics to his designs. When I consider that some bands, most notably The Grateful Dead with their Wall of Sound array of MacIntosh amps, use tube amps for voices to add harmonics, this seems plausible.  Your thoughts?

Sorry. I don't know how to use quotes and all that on this forum. No offense to anyone, but it's beyond outdated, and I've been into computers since the mid 90's.

Anyway. Thank you @ramtubes. I agree that Facebook, and Z, both suck. But you can still effectively use their ads I feel. That being said. Google Ad-sense is a great alternative.

And thank you 10 times over about the OP-amps! I've been told a million times, that it's not OP-amps, it's how they're implemented. When I say I won't buy anything with them. BS! I've got very sensitive ears. It's definitely the OP-amps. They suck arse, period! And I'll have nothing to do with them.

Hope your Thanksgiving was half as good as mine was. God bless! 
Andy B. 

ramtubes
Yes, lots of people assume that they will continue to get more power as they continue to advance the volume control.
One can be at full undistorted volume at any position of the volume control. That is just a setting of gain not power. In Asia an amplifier must play very loud at 9 o’clock or it will not sell.
I hope most of you know that volume control position has nothing to do with power or headroom. Might as well close your eyes.

I always post this one up by Nelson Pass, and some here "hate it" when I do, so just for them, here it is again.

Quote from Nelson Pass

"We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.

Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.

Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.

What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp."

I must state, before all the haters start.

The above is correct ( should have been included by Nelson Pass). If a 1:10 or more impedance ratio is met by the source and by passive to the the power amp, and in nearly all cases it is.

Save for some a small scattering of high output impedance (>1kohm) tube output sources and low input impedance (<33kohm) poweramps.

Cheers George

ramtubes
Thats horrible indeed. For some reason people buy these things.

And when I say "easy simulated speaker load" (linked) it’s made for Sterophile and modeled on the easy to drive Kantor speaker by I believe the man himself Kenneth L. Kantor It’s a pretty poor amp design that can’t stay reasonbly flat in frequency (+ - 2db) into this easy load.

Fig.4 Modified Kantor speaker simulator, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).
https://www.stereophile.com/images/archivesart/scan58.jpg

Fig.1 Circuit of Ken Kantor loudspeaker simulator, intended to represent a two-way, sealed-box minimonitor with a nominal impedance of 8 ohms.
https://www.stereophile.com/images/archivesart/scan55.jpg

Cheers George

@roberjerman

I read a report by JA measuring a Prima Luna tube amp (some years ago). He found an output impedance of 8 ohms! This means a DF of 1 ohm or less! Combined with the typical varying impedance of most speakers this is way too high! How can supposedly competent engineers get away with something like this? Because the result is far from neutral, accurate SQ! No matter how pleasing the "golden ear" crowd claims!

You are correct, 8 ohns is a very high output impedance, way too high. Why do you assume the engineers are competent? Look at the lineage of the people who designed and have promoted this amplifier.

From About us at the primaLuna web site.

The driving force behind PrimaLuna is one of high-end audio’s most astute and colorful figures, Herman van den Dungen.

WHO?

"For U.S. distribution and sales advice, he once again turned to “tube guru” and friend, Kevin Deal".

I have read several places that Kevin is the self proclaimed King Of Tubes. Ive met Kevin at CES, no crown, actually a humous guy, I wasnt expecting that. Unfortunately I understand he’s not too chatty unless you are buying.

Here, see how much of this you can take. https://www.primaluna-usa.com/about

I learned long ago that someone can make a horrible amplifier and someone will love it. This amp is not horrible, however it is not good. Given it is made in China someone is making a lot of money and its not the Chinese. We have no idea how long these amps will last. We have no idea the quality of the components. Its a big box of unknown. We do however know the mearurements which are not good at all.

Kevin has done a wonderful job of salesmanship. Note that he is the importer so he likey gets 10% for every amp coming in the country and 40% more for the ones sells directly. Go Kevin.

@roberjam

Ohm’s Law rules the amp/speaker interaction! And I agree with you that DF need not be excessively high to have adequate results!

Indeed ohm law rules everywhere. My objection is that damping factor is not damping the woofer and as long as we call it damping factor we imply we are doing something we are not.

I am one of those persons who believes language both determines and confirms that the speaker understands what he is talking about.

As long as we think damping controls a woofer we are missing the larger effect of frequency response modification.

For those still not on board, Spend $15 or just read Atkinson’s amplifier reviews, expecially the tube ones, whether you are interested in tubes or not. Please note on your subscription I sent you. John will send me a toaster when I get 10.:)

It is no secret I am interested in correcting language because it demonstrates understanding.

When did unbalanced become single ended for an input? Single ended is a type of amplifier circuit, not a connector. Who did that first? I would like to have a go at him for messing things up.

For those who do not yet know "single ended" refers to an amplifier where there is a single output tube as opposed to Push pull. How did that ever come to refer to an RCA cable? Would be more appropriate to call a single ended cable one which has just one end. I though cables had two ends.

@georgehifi 

And the same, even more so, goes for preamps, if it's loud enough that's all you need, there is no advantage to have it "able to be louder" if it's loud enough already

Yes, lots of people assume that they will continue to get more power as they continue to advance the volume control. 

One can be at full undistorted volume at any position of the volume control. That is just a setting of gain not power. In Asia an amplifier must play very loud at 9 o'clock or it will not sell. 

I hope most of you know that volume control position has nothing to do with power or headroom. Might as well close your eyes. 

To those who want a little guidance. A well balanced gain struture will play your usual listening level at noon and a bit above. If you are down at the bottom of your volume control most of the time you have too much gain and little ability to adjust it easily. Also at low settings volume controls tend to have their worst tracking between channels so the image may shift side to side at various volume settings. 

Most systems I encounter have too much gain which often results in a lot of noise. I have made attenuators for several. 

I have found that most volume controls have 20 db attenuation at noon. This means you have 20 db more SPL available...if your speaker, amplifier and ears can handle it. I find 20 dB enough to bring up even the most quiet CDs. Im not interested in 100 db SPL

@gnaudio   

I spent close to $20k on a pair of brand name monoblocks, plugged them into my dedicated 20 amp outlets and they had a loud line level hum, hired electricians, changed out grounding rods etc to the tune of $3k in costs. Took all my other equipment and cables to my dealer to make sure they weren’t the issue and they weren’t. Finally I paid $10k and bought a used amplifier and bingo the problem went away. My system is silent and absolutely glorious sounding again. The monoblocks worked at my dealer without issue but had an issue in my house. How can a designer build a product like this and what could the problem be. I am out 000’s of dollars and lots of my own time researching the issues. I borrowed isolation transformers etc as the manufacturer said it was my house that was the problem and not their amps... they were a joke to deal with and basically blew me off. The only thing they offered was to pass a name along to me if they heard of anyone wanting to buy a pair. FYI, this company has a 20 year warranty... your thoughts are appreciated. Thank you for listening to my rant...

Hey I like a good rant. I feel you man. Did you ever float the grounds on the amps? If the isolation transformers had 3 wire plugs in and out they likely carried the ground through. Sounds like you had a simple ground loop which is so common with mono amps. Two power cords, two grounds plus the preamp etc= lots of potential for hum. 

Did anyone technical ever look at your situation? Did the amps have balanced inputs available?

I take it your 10K amplifier is stereo, thus no ground loop. 

Ohm's Law rules the amp/speaker interaction! And I agree with you that DF need not be excessively high to have adequate results!

@mapman 

I do not have spl measurements but will give that a shot with my cell phone over the weekend maybe and report back.

 My concern about cell phone SPL meters is how do they know the sensitivity of your microphone. Is there one specific to your phone?

You have some nice equipment, no SPL meter?:( bad bad 

Let me know when you get one. The RadioShack  is known to be quite accurate. Hope its still available. Velleman has one too I have both the digital and analog RS meters and have tested them extensively. I just use my phone to tell when BART exceeds 100 Spl. Dont trust it for more than that even though its an Iphone. 

Whats more important is to get a peak reading meter of scope and get down to business.

I read a report by JA measuring a Prima Luna tube amp (some years ago). He found an output impedance of 8 ohms! This means a DF of 1 ohm or less! Combined with the typical varying impedance of most speakers this is way too high! How can supposedly competent engineers get away with something like this? Because the result is far from neutral, accurate SQ! No matter how pleasing the "golden ear" crowd claims!

@stfoth... where do these forum name  come from?

Hello, RM! You mentioned the recent measurements of the Cary SLI100. Reminds me a bit of one a few years back on the 300SEI.

https://www.stereophile.com/content/cary-audio-design-cad-300sei-integrated-amplifier-page-3

That's something of a sort of classic amp with quite a few fans.
Compound question.
Your thoughts on Dennis Had and legacy Cary gear?
Your thoughts on the disparity between the measurements and folks who say things like that in the subjective review?

I believe Dennis was a RF engineer that switched to audio. His first amp with the torroid output transformers was a quickly discontinued disaster. He should have know torroids are good for RF but no good for audio ouput. He learned though. I dont know anything about the legacy gear. Got a link?

Anyone who thinks a gapless torroid is good for an audio output transformer is kidding himself. Luckily few exist. 

Not sure i understand the second question. Can u clarify and expand?

@btp24

Roger, why is damping such an outdated term? ;-) I have heard you speak of how even a low output impedance amp doesn't, contrary to common believe, "damp" a woofer. You have quoted Paul Klipsch on the subject, as I recall.

As Paul said, What does it matter if you have some ohm or so of external resistance in series with 6 ohms of voice coil resistance?   

Its how output impedance affects and modifies the frequency response that we need look at. Its so obvious. That happens to be the first thing in every Stereophile test report. JA knows and he tells. Its fun to read the manufacturers response to high output impedance. They have no excuse but to make something up. 

Low damping amplifiers will bump up the bass at the resonant frequency of the speaker by providing extra voltage that is undesirable. One bump for sealed, two for ported. 

So we really aren't damping anything, are we?

@mapman

I use the receivers only as a simple demonstration of the benefits of more clean power in a line that otherwise is mostly similar in design.

Just my gut feel but I suspect there are many who have underpowered systems that clip perhaps in often subtle ways and then blame the results on a bad recording and never know it. Been there, done that myself in the past for sure as well.

Whereas not taking chances with clipping even in its most subtle form is perhaps the single biggest key to getting the best possible results. That and keeping noise to a minimum which is much harder to do in any high power integrated amp or receiver with more circuit and components in closer proximity to each other compared to separate devices

Sorry but this is not consistant with my experience. 

I find from conversations with customers that they are actually using only a fraction of the power they think they are using. In otherwords they have tons of headroom they did not think they have. Once again we do have tools to measure these things and guessing is just not good. Happy to hear any numbers you care to share in your system.

I studied clipping in many classic amplifiers and in my own of course. When tube amplifiers clip they often take a long time to recover. The highly respected HK Citation tube amps are horrible clippers with very slow recovery, the ST-70 is not so good either but recovers faster. A few amps that handle clipping softly with virtually no recovery time are the Marantz and so few others I cannot even recall them. I have measured over 100  power amps in 400 pages of notes. Before I embarked on the RM-9 I had the opportunity to play with a Marantz 5 which is a mono 8. It blew me away comparet to the Dynaco and other amps I had measured. When I designed the RM-9 I was very interested in doing as well as Marantz (SId Smith) and I feel I did. Sid Smith set a standard that might just be unbeatable for clipping and recovery. I would say if you amp never never clips you have too much amp.

So to sum it up. Good amps can clip a bit, Most people don't here clipping if it is gentle and recovers fast. Extreme headroom means nothing and may acually be a detriment due to making an amplifier far larger than it need be. I have never found a good argument for excess in anything. Thats just philosophical. I like to live lightly on this Earth. Over powered systems impress me not.

I spent close to $20k on a pair of brand name monoblocks, plugged them into my dedicated 20 amp outlets and they had a loud line level hum, hired electricians, changed out grounding rods etc to the tune of $3k in costs. Took all my other equipment and cables to my dealer to make sure they weren’t the issue and they weren’t. Finally I paid $10k and bought a used amplifier and bingo the problem went away. My system is silent and absolutely glorious sounding again. The monoblocks worked at my dealer without issue but had an issue in my house. How can a designer build a product like this and what could the problem be. I am out 000’s of dollars and lots of my own time researching the issues. I borrowed isolation transformers etc as the manufacturer said it was my house that was the problem and not their amps... they were a joke to deal with and basically blew me off. The only thing they offered was to pass a name along to me if they heard of anyone wanting to buy a pair. FYI, this company has a 20 year warranty... your thoughts are appreciated. Thank you for listening to my rant...

@georgehifi 

Just look at the frequecy response into a quite easy simulated speaker load!! that’s unacceptable, over 5db variation. no power at 200hz and at 4.5khz, nothing below 50hz and above 10khz, and two peaks at 60hz and 1.5khz
https://www.stereophile.com/images/archivesart/cad300fig1.jpg

Thats horrible indeed. For some reason people buy these things. 

Keep em coming. Lets try to drive this problem home. When everyone gets it we can stop. Does everyone here know the 100th Monkey story?

@vdotman 

Just wanted to say hello from someone who knew you back in the day when you were at Audio Art in Richmond. I really like the fact that you are sharing your craft and are encouraging dialogue with those who share your passion.
dale grigg

Hi Dale, To me those were the days that were most interesting of this hobby. We opened the store in 1975 when high end was just a whisper. We carried all the ESLs, had a separate where no cones were allowed, even had several of the classics come throught the store. I went to Vegas CES when it was in the unfinished Jockey Club. Things were way more fun then. 

Im sorry to say that 90% of what is being made today is barely interesting. In the late 70's really dedicated people like Beveridge, Bongo Jim, Arnie, and a few others were doing great work. 

 Amusing people like Robert Fulton (first person to sell me wire over dinner), Bono Jim (Incredible SS designer and most amusing person one could imagine), Jim Strickland (the acoustat speaker was pretty darn good) and most amusing and still at it Mike Moffat. I had the honor of knowing all these guys. 

Somewhere I have a picture of a BBQ at my house in Santa Barbara with Bongo Jim, Bascolm King, and a few others. I will try to find it.

Reminds me a bit of one a few years back on the 300SEI.

Just look at the frequecy response into a quite easy simulated speaker load!! that’s unacceptable, over 5db variation. no power at 200hz and at 4.5khz, nothing below 50hz and above 10khz,  and two peaks at 60hz and 1.5khz
https://www.stereophile.com/images/archivesart/cad300fig1.jpg

Cheers George

Roger,
Just wanted to say hello from someone who knew you back in the day when you were at Audio Art in Richmond. I really like the fact that you are sharing your craft and are encouraging dialogue with those who share your passion.
dale grigg

Excess headroom is a myth," at least as far as I am concerned.

Best regards,
-- Al

And the same, even more so, goes for preamps, if it's loud enough that's all you need, there is no advantage to have it "able to be louder" if it's loud enough already 

Cheers George 

Question: Tube Phono preamp. Would replacing the 1N4007 diodes (in bridge config) in power supply with HEXFREDs or Schottkys improve it? The bridge feeds a CRC filter which then feeds a tube regulator. Thanks.

Not my exact pair but there is a pic of the OHm f5 series 3 speakers on this page and mine are identical. 

http://www.e-bnlcafe.com/audioweb/speakers.htm

"Some" would be right of course. 😉

I often listen to peaks a lot louder. You would have to talk very loudly even sitting next to me to be heard. But it never actually sounds that loud which is usually a good omen that distortion is well under control.

System is OHM F5 series 3 speakers (12" Walsh style drivers in refurbed vintage OHM F cabs), Bel Canto ref1000m amps, 500 w/ch into 8 ohm, 1000 into 4 ohm. Room is 20x30 L shaped with speaks in base of L facing toward the long dimension. I normally sit about 10-12 feet back from speakers but they are quite omnidirectional so my listening location can vary.


Sometimes I sit ~4 feet in front and slightly to the left of the left speaker to get a more up close perspective. You can actually do that and retain a coherent  soundstage from most any perspective with these speakers which is perhaps their most unique feature.

I do not have spl measurements but will give that a shot with my cell phone over the weekend maybe and report back.

@mapman 

Lifelike SPL for me is that what one might hear at a similar live performance in the good seats, not too close but not too far away.

I want my gear to be able to handle it all including perhaps sitting close to the percussion at the symphony or in small club proximity to a rock band. I want to be able to hear it all. I might not be able to in reality but if I can be convinced its very close in my own unique room then that is good enough.

At the same time I want to preserve my sense of hearing so most of the time I would strive to avoid SPLs higher than the mid 80s or so. But I want my system to do it all and never break a sweat no matter what I may ask of it at any given time. That was a key design goal in putting together the setup I’ve had now for several

Ok, some would say mid 80's is lower than a symphony close up. What are your peaks?

My system doesnt sweat but i know its limits via an oscilloscope on my equipment rack. It lets me see how close I get to clipping on various music. 

Would you like to share what you have put together along with some important numbers like speaker SPL/watt, Amp power, Listening distance, anything else?

Ramtubes 11-22-2018

@almarg

It would help to quote the original question so we can follow this.

It appears to be an answer but im not getting it.

Roger, my previous post was a response to your post that immediately preceded it, about the need or lack thereof for large amounts of amplifier headroom.

And implicit in my post was agreement with your earlier statement that "over 100 watts is only justified by either high listening levels or insensitive speakers or both together. Excess headroom is a myth," at least as far as I am concerned.

Best regards,
-- Al

Lifelike SPL for me is that what one might hear at a similar live performance in the good seats, not too close but not too far away.

I want my gear to be able to handle it all including perhaps sitting close to the percussion at the symphony or in small club proximity to a rock band. I want to be able to hear it all. I might not be able to in reality but if I can be convinced its very close in my own unique room then that is good enough.

At the same time I want to preserve my sense of hearing so most of the time I would strive to avoid SPLs higher than the mid 80s or so. But I want my system to do it all and never break a sweat no matter what I may ask of it at any given time. That was a key design goal in putting together the setup I’ve had now for several years.

I use the receivers only as a simple demonstration of the benefits of more clean power in a line that otherwise is mostly similar in design.

Just my gut feel but I suspect there are many who have underpowered systems that clip perhaps in often subtle ways and then blame the results on a bad recording and never know it.   Been there, done that myself in the past for sure as well. 

Whereas not taking chances with clipping even in its most subtle form is perhaps the single biggest key to getting the best possible results. That and keeping noise to a minimum which is much harder to do in any high power integrated amp or receiver with more circuit and components in closer proximity to each other compared to separate devices.

@donjr 

A friend of mine loves Accuphase. I have seen inside and its beautifully built, measures well but its just too many parts. Their preamp has something like 600 transistors and 1200 diodes. Im into simple circuits. 

Sure would love to see the specs and a review but only with measurements.

Roger, why is damping such an outdated term? ;-) I have heard you speak of how even a low output impedance amp doesn't, contrary to common believe, "damp" a woofer. You have quoted Paul Klipsch on the subject, as I recall.

@almarg 

It would help to quote the original question so we can follow this. 

It appears to be an answer but im not getting it.

@mapman 

Back in the 70s selling most popular receiver lines from Pioneer to sansui to Tandberg the more powerful models in a line  (generally up to 120 w/ch or so) ALWAYS sounded better at least at moderate or higher levels.
Clipping is always public enemy #1 to good sound. Avoid at all costs. Better to have overkill than clip on that great sounding full range dynamic recording.
Modern louder recordings are more prone to clip as well being louder overall so that ups the ante even more when it comes to how much power might be needed.
Also music not reproduced at lifelike volumes is not accurate reproduction rather a scaled down one. Nothing wrong with listening at lower levels but one is not even attempting to reproduce real music accurately that way.

I agree with you. I worked on a lot of pioneer and such. Receivers are value products. I respect them, have worked on possible 500 in 3 years as a busy beaver. After about 80 watts I see no good reason to buy a big receiver, thats the time to go separates. 

I have found the following. Using a scope to determine clipping I find that most people do not hear clipping till it reached 10 % of the time and those are just little Millisecond clips. Longer clips are more notiable because they block the signal for a long time. So how much overkill is needed? Recievers are not designed for overkill. I use a nice Marantz 2235 in my lab for background music. Way more than I need for my Rogers LS3/5As.

I would say louder recordings are prone to less clipping because they are more compressed. Your ideas?

What is a lifelike SPL for you? On what music?

@georgehifi

https://www.stereophile.com/content/leben-cs300-integrated-amplifier-measurements

JA does make mention of the ultrasonic resonance, but "maybe" because they’re an advertiser, didn’t make too big a deal of it.

Thanks for the link. When saw the picture again my mind went.. Ah, is this Luxman? Looks like Luxman. Does perform like Luxman. Must not be Luxman.

This amplifier is a strange combination of thoughts and performance. While the bass rolls off with out the boost, the boost is enormous when used and nothing in between.

Of course it didnt do the Quads well, "no bass grip". What did you expect when the output impedance is so high and I did not say damping. I want the word damping to go away as it is a most misleading term.

Look at horrible distortion curves at even low power. The only reason anyone could like this amp is on high sensitivity speakers like Art’s and at low levels. After a watt this amp is a mess.

I have been waiting someone who really wants to know ask me why damping is such an outdated term.

Back in the 70s selling most popular receiver lines from Pioneer to sansui to Tandberg the more powerful models in a line (generally up to 120 w/ch or so) ALWAYS sounded better at least at moderate or higher levels.


Clipping is always public enemy #1 to good sound. Avoid at all costs. Better to have overkill than clip on that great sounding full range dynamic recording.

Modern louder recordings are more prone to clip as well being louder overall so that ups the ante even more when it comes to how much clean power might be needed.

Also music not reproduced at lifelike volumes is not accurate reproduction rather a scaled down one. Nothing wrong with listening at lower levels but one is not even attempting to reproduce real music accurately that way.

Class D amps may be the most practical ticket to great sound along these lines for many these days that may have never really had one before. Good ones these days sound great, tend to be smaller and more managable, are often more cost effective per watt especially when more power is called for, and are most efficient which lowers power bills and TCO.

@terry9  

Thanks for all your help, Roger. You really have opened up a stack of stuff for me to do. Much, much appreciated.

Hate to be pedantic, but I think that the 45uF figure should be 4.5uF, which is less of a problem: (75**2)  *  (800  *  10**-12)  = 4.5  *  10**-6. Your other concerns with the Vanderveen (got it right this time?) transformer remain an area of intense interest (and research!) to me. Thanks again!

You are indeed correct, it is 4.5 uF and still too much.  What raised my flag was that when i measured my speaker was at 80 pF for the 3.5 sq ft panel and I managed to make a transformer with about the same 80 pF capacitance and at 200 to 1 step up. Not much point in going further than that as half the power is in each. However had I used the plitron the numbers would be 90% of the energy absorbed by the transformer and 10% to the speaker. Thats a bad deal. 

Have you measured your drive capacitance? It is simply what you get stator to stator with a cap meter. I knew it when I was Direct Driving my 63's but that was 10 years ago. 

Not sure they still do but the 63's have a big 220 UFelectyrolytic cap in series with the hot speaker terminal to block DC. Do they still have this in some or all models? I could never understand why so large when 10 uf PPN would do.

@ieales A balanced input is no guarantee of better sonics. The devil is in the details.Every audiophile should read Bill Whitlock’s AES paper"An Overview of Audio System Grounding and Interfacing" available here https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

Thanks for the link.. Its 212 pages of slides. Power point :( I hope he takes breaks with refreshments. This could take hours. Id need 3 cocktails and a sandwich.

Can you direct us to a few pages with some meat on the bone. Im sure there is some wisdom there.

@bdp24 

@jcder, everyone is going to recommend his own pre in answer to your question. Here are a couple to consider: There is a Hovland HP-100 listed on Audiogon right now (at an asking price of $2350), a fine line stage (I heard it in Brooks Berdan’s reference system for quite a while). The EAR-Yoshino 868L line stage, another good one, occasionally pops up for around $3,000. The 868 has one true balanced (via transformer) XLR input, if that matters to you. EAR Designer Tim de Paravicini very much strikes me as the UK’s equivalent of Roger Modjeski; old school EE’s with good ears and lots of knowledge and talent.

Happy Thanksgiving. May I remind everyone the purpose of this thread is to ask a technical question, not to discuss whose preamp is better.

This is the only time I will say this and I will ignore future preamp comparisons. 

There is a lot to this question so lets hear back from you and others.

My own philosophy is based on the expectation, generally speaking, that for a given level of quality, and within a given architecture (solid state, tube push-pull, tube SET, etc.) and class of operation (A, AB, D, etc.), there will tend to be at least a loose correlation between amplifier power capability and amplifier cost. And in choosing an amplifier I prefer to direct as high a percentage as possible of the amount I want to spend toward quality, rather than toward watts.

My listening includes a lot of well engineered classical symphonic recordings, which therefore have very wide dynamic range, and not infrequently reach brief dynamic peaks approaching 105 db at the listening position. So I choose an amplifier that in conjunction with my speakers can comfortably support that level, with a few db to spare, and I don’t pay for any more watts than are necessary to accomplish that. Instead, I try to direct whatever $ I choose to invest in an amplifier toward quality, as much as possible and as best as I can determine that based on research and listening.

On another note, happy Thanksgiving to all!

Best regards,
-- Al

@pryso

Roger, really appreciate your efforts with this post. But, a question -

"Over 100 watts is only justified by either high listening levels or insensitive speakers or both together. Excess headroom is a myth."

I and many others find headroom seems to relate to clean (undistorted) dynamics. Would you expand on your myth statement, why you feel that is the case? Maybe the key is "excess"?

Thank you for bringing this up. Ive been waiting for this.

Answer is I cant say what you are hearing. I dont know if you are clipping sometimes or not. If you have a scope or peak reading voltmeter you could find out.

Now here is what i DO know. A 1000 watt amplifier played at 1 watt is likely overkill, though I had one Japanese man express this headroom is necessary. I responded, large amplifiers played at low levels may not be as good as smaller amplifiers. Many people feel small amplifiers sound better when they are enough.

Amplifier designers have to commit certain "sins" when making really big amps. High power tubes amps are enormous with enormous transformers. Take the JA200 for instance. Theres a big sin in that amp. It plays 200 watts cleanly up to 500 hz or so. As you go up the power bandwith is reduced every octave. At 20 KHZ it does just a few watts. I have measured it. Go look at the 4 chassis of that amplifier. Yet this ampifier has good reviews and hardly anyone knows about this problem. Did JA get hold of one? IDK?

Tube amplifiers scale up pretty much pound for pound for watt. 500 watts is 5 times heavier than 100 watts. Again look at the Jadis. BTW that power rolloff is entierly intentional. I could easily modify that amp to have full power to 20KHZ. The transformers are excellent. Why they chose to roll off the power I dont know, I dont speak French. Im happy to fix one up for anyone interested.

So i ask you, how many watts do you have and how many are used at your average listenting level. The headroom on CDs is well defined and easy to measure. The ones that play loud likely have 10 db. Good ones have 20dB not much more or they sound too soft.

There is a lot to this question so lets hear back from you and others.

@amb3cog

I’m willing to bet that Burning Amp alone will help. I know you can’t just spend, spend, spend, but maybe some directed advertising on Facebook towards people that are very interested in learning electronics would help. You might pick up done young people struggling to afford College? Something different should be tried, either way. Because if the word doesn’t get out. No one will ever know. It’s that simple. I only found out about the school, because I was on your site, for instance. I think it’s a great thing you’re offering, either way, and bless you for doing so sir.

Thanks for the complilment and advice. I have never looked into advertising and that is a good idea. I might give FB a try but I am not happy with what Mr. Z had done and how he is handling it. Horribly irresponsible. Ive bought puts on FB. I think FB has been a miserable failure. I think the stock price is reflecting that. 

Does anyone have suggestions on an alternative site to use for adverts? There must be lots.

I put up flyers all over the EE department at UC Berkeley. They have a total of 1000 undergrad and grad students. The flyers stayed up for several months, i checked. I got not one response. I know what is going on there and its sad. I have visited the labs, lectures, was invited by one prof to announce my school in front of his class of 150 students. I think I got one from the 150 to visit.

College students these days just want to get a diploma. Its their ticked to a high paying job. I like the Asian students, they are bright, however they might get a better education back home. They come here for the prestiege of a UC or Stanford degree. I went to Stanford, it was disappointing. UVA was far better.

The grad students who write the labs keep using the negative input of an op amp. This is not what we do in industry and it only takes a minuite to show why we dont, its noisy. Whats the chance of me correcting that? Similar labs are going at UC Davis and perhaps all UC. Thats a lot of students.

Roger, really appreciate your efforts with this post.  But, a question -

"Over 100 watts is only justified by either high listening levels or insensitive speakers or both together. Excess headroom is a myth."

I and many others find headroom seems to relate to clean (undistorted) dynamics.  Would you expand on your myth statement, why you feel that is the case?  Maybe the key is "excess"?

Yes the Beveridge RM-1 with RM-2 power supply. A legendary component in my opinion with 2 phono inputs. Roger broke the mold with this one. If you have a chance to buy one get it, they show up for around $1000 on eBay. It will most likely need to be refurbished but all in you will have a full function line stage that will rival anything out there regardless of cost.

@jcder, everyone is going to recommend his own pre in answer to your question. Here are a couple to consider: There is a Hovland HP-100 listed on Audiogon right now (at an asking price of $2350), a fine line stage (I heard it in Brooks Berdan’s reference system for quite a while). The EAR-Yoshino 868L line stage, another good one, occasionally pops up for around $3,000. The 868 has one true balanced (via transformer) XLR input, if that matters to you. EAR Designer Tim de Paravicini very much strikes me as the UK’s equivalent of Roger Modjeski; old school EE’s with good ears and lots of knowledge and talent.

could you provide a quick list of your favorite (currntly available) tube preamps?

I don't know about Roger, but the best bag for buck for me is the Schiit Freya it has everything, it's three preamps in one to suit all "flavours" and it has probably the best mechanical volume control you can get.
 And Mike Moffat is no design slouch, his designs made Theta audio what it was when it was on top, now it's gone by the wayside just like Rowland Krell ect, when the real designers left or sold out, and the accountants moved in.
What Mike has done is given the goods on the inside with the Schiit brand but the outside is low cost utilitarian, so the customer is not paying $KKK's for CNC machined polished chassis, that do nothing for the sound.
http://www.schiit.com/products/freya

Cheers George 

Fascinating thread.  Thank you!   If you dont mind, could you provide a quick list of your favorite (currntly available) tube preamps?   I don't need a phono stage.   It will need it to accept input from my PS Audio DAC, and to drive my vintage Audio Research (sorry) tube amp.   For what it's worth, I do plan to ultimately sell the AR amp and upgrade to a different make...   

Thanks for all your help, Roger. You really have opened up a stack of stuff for me to do. Much, much appreciated.

Hate to be pedantic, but I think that the 45uF figure should be 4.5uF, which is less of a problem: (75**2)  *  (800  *  10**-12)  = 4.5  *  10**-6. Your other concerns with the Vanderveen (got it right this time?) transformer remain an area of intense interest (and research!) to me. Thanks again!

Keep in mind just because a unit has a XLR input that is no assurance that the input is balanced.

A balanced input is no guarantee of better sonics. The devil is in the details.
Every audiophile should read Bill Whitlock's AES paper
"An Overview of Audio System Grounding and Interfacing" 
available here  https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf 

What is the difference between high current and high watt per channel amps. Some amps seem to advertise high watt output but don't have much current it gets confusing.

If an amplifier is class A/B implementation does it not matter to mention the Class A bias i.e how many first watts are class A. Does crossover distortion matter?. If not why and if yes what do Class A/B designers do to make it go away or mitigate it. 

Generally reading around good Class A/B amps that have high bias seem to be well reviewed. Again interested to learn more about this.